A larger gun's nominal range was useful only if its crew could see a target far enough away. A cruiser submarine sat close to the water, limiting the view from its lookouts. Destroyers and sloops had higher lookouts that could let them see far enough to exploit their guns' range. Practical engagement ranges could therefore be similar, and the escort might even hold the advantage. The comparison also judges the escorts' target profiles to be only moderately larger.
Notable Point · 5:49-6:22
Why a larger gun did not guarantee a longer engagement range
Low lookouts limited how far a submarine could see, allowing taller escorts to use their guns at comparable or greater practical ranges.